The present invention relates generally to physical pairing of inductively coupled devices, and more particularly to physical pairing of inductively coupled devices having magnets.
The use of wireless devices has proliferated in recent years. Not only can devices wirelessly transmit data to other devices, devices can also wirelessly supply power to other devices.
There are many applications that utilize the wireless transmission of data. One particular category of applications involves short-range or near-field transmissions, which typically occur over a distance of several feet or less. Examples of short-range or near-field transmission protocols or standards include radio-frequency identification (RFID), dedicated short-range communications (DSRC), Bluetooth, ZigBee, and near-field communications (NFC).
There are also many applications for utilizing wireless power supplies. For example, passive RFID tags may be wirelessly charged by active RFID devices and passive NFC tags may be wirelessly charged by active NFC devices. Likewise, a variety of electrical or electronic devices, including electric cars, electric toothbrushes, mobile phones, mp3 players, and the like, may be wirelessly charged using wireless charging pads, plates, stations, or other charging devices.
Electromagnetic induction may be used for wirelessly transmitting data or wirelessly supplying power from one device to another device. Typically, a first device that uses electromagnetic induction to transmit data or supply power to a second device includes a first inductive element, often a primary coil. When electric current flows through the first device's primary coil, an electromagnetic field is created. If the first device's primary coil is in proximity to a secondary coil in the second device, the primary coil's electromagnetic field may inductively couple with the second device's secondary coil, producing a current within the secondary coil. This current may be used in transmission of data or supply of power between the two devices.
For the inductive coupling to achieve high efficiency, it is typically desirable to properly align the primary coil and the secondary coil and minimize the distance between the primary coil and the secondary coil. To promote the proper alignment of, and distance between, two inductively coupled devices, the two inductively coupled devices may be physically and/or mechanically paired using, for example, magnets, gravity, groves, guides, slots, clamps, latches, cradles, or other well-known pairing techniques.
The use of magnets to pair two inductively coupled devices, however, may be problematic. A magnetic field is associated with the magnets, and an electromagnetic field is associated with the inductively coupled devices in operation. In addition, the inductive devices may themselves be magnetizable, and the magnets themselves may include material that is responsive in some way to electromagnetic field states. The magnetic field and the electromagnetic field may interfere with one another, possibly degrading performance. The magnetic field may also affect the inductive devices in such a way that degrades operation of the inductive coupling. The electromagnetic field may also affect the magnets (or their materials) in varying ways.
Widely separating in distance the inductive elements and the magnets may avoid or reduce these variations interactions. However, such a wide separation may be difficult to obtain if the devices are not physically large.